ACADIAN SLIDING AND GLIDING: ANATOMY OF STYLES FOR GRAVITATIONAL FAULT DEVELOPMENT AND HYDROCARBON MIGRATION IN THE WESTERN APPALACHIAN FORELAND BASIN OF PENNSYLVANIA AND WEST VIRGINIA
Part of the Acadian structural system in a 3D seismic survey includes 1) an upslope zone-of-removal where the basal decollement cut a linear, 1050 m wide trough downsection deep (~65m) into the Silurian Vernon shale, 2) an adjacent down-slope, slide-thickened, Vernon/Lower Salina section that exhibits spectacular box folds, kink folds, and disharmonic folds that indicate multiple decollement and thrust ramps, and 3) steeply dipping faults with down-on-the-east throw, some of which are normal faults that accommodated downslope transport with slump block back-rotation on the Vernon and F-salt section. A Late Devonian age is suggested for the decollement because Upper Devonian Elk sands onlap and infill the drape-syncline above the zone-of-removal and basement fault-influenced paleoslope changes occurred then. The thick F-salt section does not display significant thinning or thickening in the zone of removal or in the slide-thickened area of the back-rotated blocks, but is internally deformed. The primarily easterly-verging thrusts climb upsection from nickpoints primarily at the Onondaga/Helderberg or the Tully. Thrust fault-associated anticlines have F-salt and Vernon involvement.